Silicon-based cooling package for laser gain medium

ABSTRACT

Embodiments of silicon-based thermal energy transfer apparatus for gain medium crystal of a laser system are provided. For a disk-shaped crystal, the apparatus includes a silicon-based manifold and a silicon-based cover element. For a rectangular cuboid-shaped gain medium crystal, the apparatus includes a first silicon-based manifold, a second silicon-based manifold, and first and second conduit elements coupled between the first and second manifolds. For a right circular cylinder-shaped gain medium crystal, the apparatus includes a first silicon-based manifold, a second silicon-based manifold, and first and second conduit elements coupled between the first and second manifolds.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims priority from U.S. Patent Application No.61/409,211, filed in the United States Patent & Trademark Office on Nov.2, 2010, entitled “Silicon-Based Cooling Package for Laser Gain Medium”,which is hereby incorporated in its entirety by reference.

BACKGROUND

1. Technical Field

The present disclosure generally relates to the field of transfer ofthermal energy and, more particularly, to removal of thermal energy froma gain medium of a laser system.

2. Description of the Related Art

In general, a laser system is constructed with three main partsincluding an energy source, a laser medium, and two or more mirrors thatform an optical resonator. The energy source of a laser system is alsoknown as the pump source, and is the part that provides energy to thelaser system.

The laser medium of a laser system is also known as the gain medium, andis the major determining factor of various properties of the lasersystem including the wavelength of operation. The gain medium is excitedby the pump source to produce a population inversion. The gain medium isalso where spontaneous emission of photons and stimulated emission ofphotons take place that lead to the phenomenon of optical gain, oramplification. Gain media are generally made of liquids, gases, solids,or semiconductors. The solids used as gain media typically includecrystals and glasses, and may be doped with an impurity such aschromium, neodymium, erbium, or titanium ions. As the gain medium isexcited to emit photons, a large amount of thermal energy is generatedby the gain medium. Such thermal energy needs to be removed from thegain medium, by a cooling package for example, in order to prolong thelifetime of the gain medium as well as keep the laser system withinnormal operating parameters.

The optical resonator consists of two or more mirrors placed around thegain medium to provide feedback of the light. Light from spontaneousemission of the gain medium is reflected by the mirrors back into thegain medium, where the light may be amplified by stimulated emission.The light may be reflected from the mirrors and thus pass through thegain medium hundreds of times before exiting the gain medium. The designand alignment of the mirrors with respect to the gain medium is crucialto determining the exact operating wavelength and other properties ofthe laser system.

In applications where the laser system needs to be compact, one or morelaser diodes may be used as the energy source given the small formfactor of laser diodes. The gain media in such a laser systemcorrespondingly tends to have small form factor as well. However,conventional metal-based cooling package made of copper, aluminum or atype of metal alloy tend to suffer from corrosion and clogging ofcoolant channel, if liquid is used as a heat transfer medium.Additionally, at very high temperature the metal may deform if thetemperature approaches the melting temperature of the metal.

SUMMARY

In one aspect, a thermal energy transfer apparatus that removes thermalenergy from a disk-shaped gain medium crystal of a laser system includesa silicon-based manifold and a silicon-based cover element.

The silicon-based manifold has internal coolant flow channels, a firstside having coolant inlet ports and coolant outlet ports that areconnected to the internal coolant flow channels, and a second sideopposite the first side and being substantially flat to provide surfacearea to contact with a first primary surface of the crystal. Thesilicon-based cover element has an opening to expose a portion of asecond primary surface of the crystal that is opposite the first primarysurface of the crystal when the crystal is mounted between the coverelement and the manifold.

The manifold may include a first half structure made of silicon and asecond half structure made of silicon. The first half structure may havea first primary surface that is the first side of the manifold and asecond primary surface opposite the first primary surface. The firsthalf structure may have openings as the coolant inlet ports and thecoolant outlet ports of the manifold. The second primary surface of thefirst half structure may have grooves that form a first half of theinternal coolant flow channels of the manifold. The second halfstructure may have a first primary surface that is the second side ofthe first manifold and a second primary surface opposite the firstprimary surface. The second primary surface of the second half structuremay have grooves that form a second half of the internal coolant flowchannels of the manifold.

The cover element may include a first plate made of silicon and a secondplate made of silicon. The first plate may have an opening smaller thanan area of the second primary surface of the crystal to expose a portionof the second primary surface of the crystal. The second plate may havean opening larger than the area of the second primary surface of thecrystal and shaped to at least partially circumscribe the crystal withthe crystal contacting a plurality of points of the opening of thesecond plate when the crystal is mounted between the cover element andthe manifold.

The apparatus may further include a layer of synthetic diamond on thesecond side of the manifold to be in direct contact with the crystal.Alternatively, the apparatus may further include a plurality ofnanotubes on the second side of the manifold to be in direct contactwith the crystal.

The apparatus may further include an inbound coolant tubing made ofnon-corrosive material, an outbound coolant tubing made of non-corrosivematerial, an adapter made of non-corrosive material, and a heatexchanger system. The adapter may have a first side coupled to the firstside of the manifold and a second side coupled to the inbound coolanttubing and the outbound coolant tubing. The adapter may have an inboundcoolant flow channel to allow the coolant to flow from the inboundcoolant tubing to the manifold through the adapter, and an outboundcoolant flow channel to allow the coolant to flow from the manifold tothe outbound coolant tubing through the adapter. The heat exchangersystem may be coupled to the outbound coolant tubing and the inboundcoolant tubing to supply the coolant to the inbound coolant tubing andreceive the coolant from the outbound coolant tubing to remove thermalenergy from the coolant.

In another aspect, a thermal energy transfer apparatus that removesthermal energy from a rectangular cuboid-shaped gain medium crystal of alaser system includes a first silicon-based manifold, a secondsilicon-based manifold, a first conduit element, and a second conduitelement.

The first silicon-based manifold has internal coolant flow channels, afirst side having coolant outlet ports that are connected to theinternal coolant flow channels, and a second side opposite the firstside and having coolant inlet ports that are connected to the internalcoolant flow channels. The second side of the first manifold issubstantially flat to provide surface area to contact with a firstsurface of the crystal. The second silicon-based manifold has internalcoolant flow channels, a first side having coolant inlet ports that areconnected to the internal coolant flow channels, and a second sideopposite the first side and having coolant outlet ports that areconnected to the internal coolant flow channels. The second side of thesecond manifold is substantially flat to provide surface area to contactwith a second surface of the crystal. The first conduit element iscoupled between the first and second manifolds and has a cavity thatallows a portion of a coolant to flow through the first conduit elementfrom a first group of the coolant outlet ports of the second manifold toa first group of the coolant inlet ports of the first manifold. A firstside of the first conduit element is substantially flat to providesurface area to contact with a third surface of the crystal. The secondconduit element is coupled between the first and second manifolds andhas a cavity that allows a portion of a coolant to flow through thefirst conduit element from a first group of the coolant outlet ports ofthe second manifold to a first group of the coolant inlet ports of thefirst manifold. A first side of the first conduit element issubstantially flat to provide surface area to contact with a fourthsurface of the crystal.

The first manifold may include a first half structure made of siliconand a second half structure made of silicon. The first half structuremay have a first primary surface that is the first side of the firstmanifold and a second primary surface opposite the first primarysurface. The first half structure may have openings as the coolantoutlet ports of the first manifold. The second primary surface of thefirst half structure may have grooves that form a first half of theinternal coolant flow channels of the first manifold. The second halfstructure may have a first primary surface that is the second side ofthe first manifold and a second primary surface opposite the firstprimary surface. The second half structure may have openings as thecoolant inlet ports of the first manifold. The second primary surface ofthe second half structure may have grooves that form a second half ofthe internal coolant flow channels of the first manifold.

The second manifold may have a third half structure made of silicon anda fourth half structure made of silicon. The third half structure mayhave a first primary surface that is the first side of the secondmanifold and a second primary surface opposite the first primarysurface. The third half structure may have openings as the coolant inletports of the second manifold. The second primary surface of the thirdhalf structure may have grooves that form a first half of the internalcoolant flow channels of the second manifold. The fourth half structuremay have a first primary surface that is the second side of the secondmanifold and a second primary surface opposite the first primarysurface. The fourth half structure may have openings as the coolantoutlet ports of the second manifold. The second primary surface of thefourth half structure may have grooves that form a second half of theinternal coolant flow channels of the second manifold.

At least one of the first conduit element or the second conduit elementmay be made of silicon, a metal-based or ceramic material.

The apparatus may further include a layer of synthetic diamond on thesecond side of the first manifold to be in direct contact with thecrystal, and a layer of synthetic diamond on the second side of thesecond manifold to be in direct contact with the crystal.

Alternatively, the apparatus may further include a plurality ofnanotubes on the second side of the first manifold to be in directcontact with the crystal, and a plurality of nanotubes on the secondside of the second manifold to be in direct contact with the crystal.

The apparatus may further include an outbound coolant tubing made ofnon-corrosive material, an inbound coolant tubing made of non-corrosivematerial, a first adapter made of non-corrosive material, and a secondadapter made of non-corrosive material. The first adapter may have afirst side coupled to the first side of the first manifold and a secondside coupled to the outbound coolant tubing. The first adapter may havean internal coolant flow channel to allow the coolant to flow from thefirst manifold to the outbound coolant tubing through the first adapter.The second adapter may have a first side coupled to the first side ofthe second manifold and a second side coupled to the inbound coolanttubing. The second adapter may have an internal coolant flow channel toallow the coolant to flow from the inbound coolant tubing to the secondmanifold through the second adapter.

The apparatus may include a heat exchanger system coupled to theoutbound coolant tubing and the inbound coolant tubing such that theheat exchanger system supplies the coolant to the inbound coolant tubingand receives the coolant from the outbound coolant tubing to removethermal energy from the coolant.

Alternatively, the apparatus may include a coolant supplier coupled tothe inbound coolant tubing to supply the coolant at a first temperaturerange, and a coolant receiver coupled to the outbound coolant tubing toreceive the coolant at a second temperature range that is higher thanthe temperature range.

In yet another aspect, a thermal energy transfer apparatus that removesthermal energy from a right circular cylinder-shaped gain medium crystalof a laser system includes a first silicon-based manifold, a secondsilicon-based manifold, a first conduit element, and a second conduitelement.

The first silicon-based manifold has internal coolant flow channels, afirst side having coolant outlet ports that are connected to theinternal coolant flow channels, and a second side opposite the firstside and having coolant inlet ports that are connected to the internalcoolant flow channels. The second side of the first manifold has agroove to accommodate a portion of the crystal. The second silicon-basedmanifold has internal coolant flow channels, a first side having coolantinlet ports that are connected to the internal coolant flow channels,and a second side opposite the first side and having coolant outletports that are connected to the internal coolant flow channels. Thesecond side of the second manifold has a groove to accommodate a portionof the crystal. The first conduit element is coupled between the firstand second manifolds and has a cavity that allows a portion of a coolantto flow through the first conduit element from a first group of thecoolant outlet ports of the second manifold to a first group of thecoolant inlet ports of the first manifold. A first side of the firstconduit element is shaped to accommodate a portion of the crystal. Thesecond conduit element is coupled between the first and second manifoldsand has a cavity that allows a portion of a coolant to flow through thefirst conduit element from a first group of the coolant outlet ports ofthe second manifold to a first group of the coolant inlet ports of thefirst manifold. A first side of the second conduit element being shapedto accommodate a portion of the crystal.

The first manifold may include a first half structure made of siliconand a second half structure made of silicon. The first half structuremay have a first primary surface that is the first side of the firstmanifold and a second primary surface opposite the first primarysurface. The first half structure may have openings as the coolantoutlet ports of the first manifold. The second primary surface of thefirst half structure may have grooves that form a first half of theinternal coolant flow channels of the first manifold. The second halfstructure may have a first primary surface that is the second side ofthe first manifold and a second primary surface opposite the firstprimary surface. The second half structure may have openings as thecoolant inlet ports of the first manifold. The second primary surface ofthe second half structure may have grooves that form a second half ofthe internal coolant flow channels of the first manifold.

The second manifold may include a third half structure made of siliconand a fourth half structure made of silicon. The third half structuremay have a first primary surface that is the first side of the secondmanifold and a second primary surface opposite the first primarysurface. The third half structure may have openings as the coolant inletports of the second manifold. The second primary surface of the thirdhalf structure may have grooves that form a first half of the internalcoolant flow channels of the second manifold. The fourth half structuremay have a first primary surface that is the second side of the secondmanifold and a second primary surface opposite the first primarysurface. The fourth half structure may have openings as the coolantoutlet ports of the second manifold. The second primary surface of thefourth half structure may have grooves that form a second half of theinternal coolant flow channels of the second manifold.

At least one of the first conduit element or the second conduit elementis made of silicon, a metal-based or ceramic material.

The apparatus may further include a filler material such as asoft-metal, silver glass or thermal epoxy, to fill a gap of spacebetween the crystal, the first manifold, the second manifold, the firstconduit element, and the second conduit element.

The apparatus may further include an outbound coolant tubing made ofnon-corrosive material, an inbound coolant tubing made of non-corrosivematerial, a first adapter made of non-corrosive material, and a secondadapter made of non-corrosive material. The first adapter may have afirst side coupled to the first side of the first manifold and a secondside coupled to the outbound coolant tubing. The first adapter may havea coolant flow channel to allow the coolant to flow from the firstmanifold to the outbound coolant tubing through the first adapter. Thesecond adapter may have a first side coupled to the first side of thesecond manifold and a second side coupled to the inbound coolant tubing.The second adapter may have a coolant flow channel to allow the coolantto flow from the inbound coolant tubing to the second manifold throughthe second adapter.

The apparatus may include a heat exchanger system coupled to theoutbound coolant tubing and the inbound coolant tubing such that theheat exchanger system supplies the coolant to the inbound coolant tubingand receives the coolant from the outbound coolant tubing to removethermal energy from the coolant.

Alternatively, the apparatus may include a coolant supplier coupled tothe inbound coolant tubing to supply the coolant at a first temperaturerange, and a coolant receiver coupled to the outbound coolant tubing toreceive the coolant at a second temperature range that is higher thanthe temperature range.

This summary is provided to introduce concepts relating to heat removalfrom laser gain medium using silicon-based thermal energy transferpackage. These techniques are further described below in the detaileddescription. This summary is not intended to identify essential featuresof the claimed subject matter, nor is it intended for use in determiningthe scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of the present disclosure. The drawings illustrate embodiments ofthe disclosure and, together with the description, serve to explain theprinciples of the disclosure. It is appreciable that the drawings arenot necessarily in scale as some components may be shown to be out ofproportion than the size in actual implementation in order to clearlyillustrate the concept of the present disclosure.

FIG. 1 illustrates a first silicon-based thermal energy transfer devicefor a disk-shaped gain medium crystal of a laser system in accordancewith one non-limiting embodiment.

FIG. 2 illustrates a side view and a cross-sectional view of thesilicon-based thermal energy transfer device of FIG. 1.

FIG. 3 illustrates a top view and a bottom view of the silicon-basedthermal energy transfer device of FIG. 1.

FIG. 4 illustrates a second silicon-based thermal energy transfer devicefor a rectangular cuboid-shaped gain medium crystal of a laser system inaccordance with one non-limiting embodiment.

FIG. 5 illustrates a side view and a cross-sectional view of thesilicon-based thermal energy transfer device of FIG. 4.

FIG. 6 illustrates a top view and a bottom view of the silicon-basedthermal energy transfer device of FIG. 4.

FIG. 7 illustrates a third silicon-based thermal energy transfer devicefor a right circular cylinder-shaped gain medium crystal of a lasersystem in accordance with one non-limiting embodiment.

FIG. 8 illustrates a side view and a cross-sectional view of thesilicon-based thermal energy transfer device of FIG. 7.

FIG. 9 illustrates a top view and a bottom view of the silicon-basedthermal energy transfer device of FIG. 7.

FIG. 10 illustrates a first thermal energy transfer apparatus thatincludes the silicon-based thermal energy transfer device of FIGS. 1-3in accordance with one non-limiting embodiment.

FIG. 11 illustrates a second thermal energy transfer apparatus thatincludes the silicon-based thermal energy transfer device of FIGS. 4-6in accordance with one non-limiting embodiment.

FIG. 12 illustrates a third thermal energy transfer apparatus thatincludes the silicon-based thermal energy transfer device of FIGS. 7-9in accordance with one non-limiting embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Overview

The present disclosure describes embodiments of silicon-based thermalenergy transfer techniques for the gain medium crystal of a lasersystem.

While aspects of described techniques relating to silicon-based thermalenergy transfer packages for laser gain media can be implemented in anynumber of different laser systems, embodiments are described in contextof the following exemplary configurations.

Illustrative First Thermal Energy Transfer Apparatus

FIGS. 1-3 illustrate various views of a silicon-based thermal energytransfer device 100 for a disk-shaped gain medium crystal 115 of a lasersystem in accordance with one non-limiting embodiment. The device 100includes a first plate 102, a second plate 104, a first half structure108, and a second half structure 106. Each of the first plate 102,second plate 104, first half structure 108, and second half structure106 is made of silicon. In one embodiment, each of the first plate 102,second plate 104, first half structure 108, and second half structure106 is deposited with a combination of layer of metals such as, forexample, Cr/Au, TiW/Ni/Au or TiW/Au. In one embodiment, each of thefirst plate 102, second plate 104, first half structure 108, and secondhalf structure 106 is fabricated from a respective silicon wafer usingsemiconductor fabrication technology including photolithography, dryetch, wet etch, etc.

The first plate 102 has an opening 132. The opening 132 has an area thatis smaller than the area of either of the two primary surfaces of thecrystal 115. In one embodiment, the opening 132 is approximatelyoctagon-shaped as shown in FIG. 1. In other embodiments, the opening 132may have one of other shapes such as a circular shape or anotherpolygonal shape.

The second plate 104 has an opening 134. The opening 134 has an areathat is slightly larger than the area of either of the two primarysurfaces of the crystal 115. The opening 134 is shaped so that, when thecrystal 115 is placed within the opening 134, the opening 134 at leastpartially circumscribes the crystal 115 with the crystal 115 contactinga plurality of points of the opening 134. In one embodiment, the opening134 is approximately octagon-shaped as shown in FIG. 1. In otherembodiment, the opening 134 may have one of other polygonal shapes.

The first half structure 108 has a first row of openings 140 as coolantinlet ports and a second row of openings 142 as coolant outlet ports. Asshown in FIG. 3, on one of the two primary surfaces of the first halfstructure 108, there are grooves 138 each of which connecting arespective pair of one of the openings 140 and one of the openings 142.

The second half structure 106 also has a plurality of grooves 136 on oneof its two primary surfaces. Each of the grooves 136 corresponds to arespective one of the grooves 138 such that when the first halfstructure 108 and the second half structure 106 are bonded together toform a manifold, the grooves 136 and the grooves 138 form internalcoolant flow channels for a coolant flowing in through the openings 140to flow out through the openings 142. The primary surface of the secondhalf structure 106 opposite the primary surface that has the grooves 136is substantially flat to provide surface area to contact with thecorresponding primary surface of the crystal 115.

In one embodiment, the thinnest part of the second half structure 106where the grooves 136 are, denoted as thickness T1 in FIG. 2, isapproximately a range of 50 μm to 100 um. In one embodiment, thethinnest part of the first half structure 108 where the grooves 138 are,denoted as thickness T2 in FIG. 2, is approximately a range of 100 μm to200 um.

As shown in FIGS. 1 and 2, the first plate 102 and the second plate 104together form a cover element. The first half structure 108 and thesecond half structure 106 together form a manifold. The first plate 102and the second plate 104 may be affixed to each other by solder orsilicon-to-silicon bonding. The first half structure 108 and the secondhalf structure 106 may be affixed to each other by solder orsilicon-to-silicon bonding. In one embodiment, the cover element formedby the first plate 102 and the second plate 104 and the manifold formedby the first half structure 108 and the second half structure 106 aresoldered together. That is, the primary surface of the second plate 104facing the second half structure 106 is soldered to the primary surfaceof the second half structure 106 facing the second plate 104.

In various embodiments, a layer of thermally-conductive material 120 iscoated on at least the side of the manifold formed by the first halfstructure 108 and the second half structure 106 that faces the coverelement formed by the first plate 102 and the second plate 104. In oneembodiment, the layer of thermally-conductive material 120 has athickness, denoted as thickness T3 in FIG. 2, of approximately a rangeof 25 to 300 μm. When the crystal 115 is mounted between the coverelement formed by the first plate 102 and the second plate 104 and themanifold formed by the first half structure 108 and the second halfstructure 106, the primary surface of the crystal 115 that is notexposed is in direct contact with the layer of thermally-conductivematerial 120. The layer of thermally-conductive material 120 needs tohave good conductive thermal efficiency to maximize thermal energy inthe crystal 115 to be transferred to the second half structure 106. Thelayer of thermally-conductive material 120 also relieves the thermalstress between the crystal 115 and the second half structure 106 whenthere is a temperature differential between the crystal 115 and thesecond half structure 106. In one embodiment, the layer ofthermally-conductive material 120 is a layer of synthetic diamond. Thelayer of synthetic diamond may be of black color (with thermalconductivity of 800 to 1200 W-deg/m) or, alternatively, translucentcolor (with thermal conductivity of 1200 to 2000 W-deg/m). In anotherembodiment, the layer of thermally-conductive material 120 includes aplurality of nanotubes.

As shown in FIGS. 1 and 2, when the disk-shaped crystal 115 is mountedbetween the cover element formed by the first plate 102 and the secondplate 104 and the manifold formed by the first half structure 108 andthe second half structure 106, a portion but not all of a primarysurface of the crystal 115 is exposed. With one primary surface of thecrystal 115 exposed to a laser beam and the opposite primary surface ofthe crystal 115 in direct contact with the layer of thermally-conductivematerial 120 coated on the second half structure 106, the laser beam isrefracted a number of times, and thereby being amplified, within thecrystal 115 before a laser beam with increased energy is reflected outof the crystal 115 as shown in FIG. 1.

FIG. 10 illustrates a thermal energy transfer apparatus 1001 thatincludes the silicon-based thermal energy transfer device 100 inaccordance with one non-limiting embodiment. The apparatus 1001 includesan inbound coolant tubing 180, an outbound coolant tubing 182, anadapter 170, and a heat exchanger system 190.

The adapter 170 has a first side coupled to the first side of the firsthalf structure 108 that has the openings 140 and 142, and a second sidecoupled to the inbound coolant tubing 180 and the outbound coolanttubing 182. The adapter 170 has an inbound coolant flow channel (notshown) to allow the coolant to flow from the inbound coolant tubing 180to the manifold formed by the half structures 106 and 108 through theadapter 170. The adapter also has an outbound coolant flow channel (notshown) to allow the coolant to flow from the manifold formed by the halfstructures 106 and 108 to the outbound coolant tubing 182 through theadapter 170.

The heat exchanger system 190 is coupled to the outbound coolant tubing182 and the inbound coolant tubing 180. The heat exchanger system 190supplies the coolant to the inbound coolant tubing 180 and receives thecoolant from the outbound coolant tubing 182 to remove thermal energyfrom the coolant. In one embodiment, the coolant is de-ionized water. Inother embodiments, the coolant may be other suitable fluid such as, forexample, distilled water, water-alcohol mixture, or water-glycolmixture.

Each of the inbound coolant tubing 180, outbound coolant tubing 182, andadapter 170 is respectively made of a non-corrosive material. In oneembodiment, each of the inbound coolant tubing 180 and outbound coolanttubing 182 is respectively made of stainless steel, a nickel-platedmetallic material, a gold-plated metallic material, or a ceramicmaterial. In one embodiment, the adapter 170 is made of a ceramicmaterial. The materials that the inbound coolant tubing 180, outboundcoolant tubing 182, and adapter 170 are made of cannot be plastics orany material subject to corrosion when exposed to water. Chemicalsleaching out of plastics or particles coming off of a material due tocorrosion, when any of the inbound coolant tubing 180, outbound coolanttubing 182, or adapter 170 is made of plastics or a corrosive material,will likely foul or clog up the internal coolant flow channels of themanifold formed by the first half structure 108 and second halfstructure 106 as well as the heat exchanger system 190.

In one embodiment, the inbound coolant tubing 180 and the outboundcoolant tubing 182 are coupled to the adapter 170 by solder, press-fit,epoxy bonding, or single-body machined. In one embodiment, the adapter170 is coupled to the second half structure 108 by solder or epoxybonding.

Illustrative Second Thermal Energy Transfer Apparatus

FIGS. 4-6 illustrate various views of a silicon-based thermal energytransfer device 400 for a rectangular cuboid-shaped gain medium crystal415 of a laser system in accordance with one non-limiting embodiment.The device 400 includes a first half structure 402, a second halfstructure 404, a third half structure 406, a fourth half structure 408,a first conduit element 450 a, and a second conduit element 450 b. Eachof the first half structure 402, second half structure 404, third halfstructure 406, and fourth half structure 408 is made of silicon. In oneembodiment, each of the first half structure 402, second half structure404, third half structure 406, and fourth half structure 408 ismetal-plated with a metal such as, for example, gold.

In one embodiment, each of the first half structure 402, second halfstructure 404, third half structure 406, and fourth half structure 408is fabricated from a respective silicon wafer using semiconductorfabrication technology including photolithography, dry etch, wet etch,etc. In one embodiment, the first half structure 402 and the fourth halfstructure 408 are identical, and therefore can be made by the samefabrication process and even be from the same silicon wafer. Likewise,in one embodiment, the second half structure 404 and the third halfstructure 406 are identical, and therefore can be made by the samefabrication process and even be from the same silicon wafer.

The first half structure 402 has a row of openings 446 as coolant outletports. As shown in FIG. 6, on one of the two primary surfaces of thefirst half structure 402, there are grooves 436 each of which associatedwith a respective one of the openings 446. The second half structure 404has a first row of openings 441 a and a second row of openings 441 b ascoolant inlet ports. As shown in FIG. 6, on one of the two primarysurfaces of the second half structure 404, there are grooves 438 each ofwhich connecting a respective pair of one of the openings 441 a and oneof the openings 441 b. The primary surface of the second half structure404 opposite the primary surface that has the grooves 438 issubstantially flat to provide surface area to contact with thecorresponding primary surface of the crystal 415.

In one embodiment, the thinnest part of the second half structure 404where the grooves 438 are, denoted as thickness T6 in FIG. 5, isapproximately a range of 50 to 100 μm.

The fourth half structure 408 has a row of openings 440 as coolant inletports. As shown in FIG. 6, on one of the two primary surfaces of thefourth half structure 408, there are grooves 437 each of whichassociated with a respective one of the openings 440. The third halfstructure 406 has a first row of openings 442 a and a second row ofopenings 442 b as coolant outlet ports. As shown in FIG. 6, on one ofthe two primary surfaces of the third half structure 406, there aregrooves 439 each of which connecting a respective pair of one of theopenings 442 a and one of the openings 442 b. The primary surface of thethird half structure 406 opposite the primary surface that has thegrooves 439 is substantially flat to provide surface area to contactwith the corresponding primary surface of the crystal 415.

In one embodiment, the thinnest part of the third half structure 406where the grooves 439 are, denoted as thickness T5 in FIG. 5, isapproximately a range of 50 to 100 μm.

As shown in FIGS. 4 and 5, the first half structure 402 and the secondhalf structure 404 together form a first manifold. The third halfstructure 406 and the fourth half structure 408 together form a secondmanifold. The first half structure 402 and the second half structure 404may be affixed to each other by solder, silicon-to-gold eutecticbonding, or silicon-to-silicon bonding. The third half structure 406 andthe fourth half structure 408 may be affixed to each other by solder,silicon-to-gold eutectic bonding, or silicon-to-silicon bonding.

The first conduit element 450 a has a cavity 444 a. The second conduitelement 450 b has a cavity 444 b. When the first and second conduitelements 450 a and 450 b are coupled between the first manifold formedby the first and second half structures 402 and 404 and the secondmanifold formed by the third and fourth half structures 406 and 408, thecavities 444 a and 444 b allow a coolant to flow through the first andsecond conduit elements 450 a and 450 b from the openings 442 a and 442b, which are the coolant outlet ports of the second manifold formed bythe third half structure 406 and the fourth half structure 408, to theopenings 441 a and 441 b, which are the coolant inlet ports of the firstmanifold formed by the first half structure 402 and the second halfstructure 404. In one embodiment, one or both of the first and secondconduit elements 450 a and 450 b are made of a metal-based material suchas, for example, copper, aluminum, or stainless steel. In oneembodiment, one or both of the first and second conduit elements 450 aand 450 b are made of a ceramic or silicon material.

In various embodiments, a layer of thermally-conductive material 420 ais coated on at least the side of the first manifold formed by the firstand second half structures 402 and 404 that faces the second manifoldformed by the third and fourth half structures 406 and 408. In oneembodiment, the layer of thermally-conductive material 420 a has athickness, denoted as thickness T7 in FIG. 5, of approximately a rangeof 100 to 200 μm. When the crystal 415 is mounted between the firstmanifold formed by the first and second half structures 402 and 404 andthe second manifold formed by the third and fourth half structures 406and 408, one of the primary surfaces of the crystal 415 is in directcontact with the layer of thermally-conductive material 420 a.

Similarly, in various embodiments, a layer of thermally-conductivematerial 420 b is coated on at least the side of the second manifoldformed by the third and fourth half structures 406 and 408 that facesthe first manifold formed by the first and second half structures 402and 404. In one embodiment, the layer of thermally-conductive material420 b has a thickness, denoted as thickness T4 in FIG. 5, ofapproximately 100 to 200 μm. When the crystal 415 is mounted between thefirst manifold formed by the first and second half structures 402 and404 and the second manifold formed by the third and fourth halfstructures 406 and 408, one of the primary surfaces of the crystal 415is in direct contact with the layer of thermally-conductive material 420b.

The layers of thermally-conductive material 420 a and 420 b need to havegood conductive thermal efficiency to maximize thermal energy in thecrystal 415 to be transferred to the second half structure 404 and thethird half structure 406. The layers of thermally-conductive material420 a and 420 b also relieve the thermal stress between the crystal 415and the second half structure 404 and the third half structure 406 whenthere is a temperature differential between the crystal 415 and thesecond half structure 404 and the third half structure 406. In oneembodiment, at least one of the layers of thermally-conductive material420 a and 420 b is a layer of synthetic diamond. The layer of syntheticdiamond may be of black color (with thermal conductivity of 800 to 1200W-deg/m) or, alternatively, translucent color (with thermal conductivityof 1200 to 2000 W-deg/m). In another embodiment, at least one of thelayers of thermally-conductive material 420 a and 420 b includes aplurality of nanotubes.

As shown in FIGS. 4 and 5, when the rectangular cuboid-shaped crystal415 is mounted between the first manifold formed by the first and secondhalf structures 402 and 404, the second manifold formed by the third andfourth half structures 406 and 408, and the first and second conduitelements 450 a and 450 b, four of the six primary surfaces of thecrystal 415 are in contact with the device 400, leaving two of the sixprimary surfaces of the crystal 415 exposed to allow a laser beam toshine through.

FIG. 11 illustrates a thermal energy transfer apparatus 4001 thatincludes the silicon-based thermal energy transfer device 400 inaccordance with one non-limiting embodiment. The apparatus 4001 includesan inbound coolant tubing 480, an outbound coolant tubing 482, a firstadapter 470 a, and a second adapter 470 b.

The first adapter 470 a has a first side coupled to the first side ofthe first manifold, formed by the first and second half structures 402and 404, and a second side coupled to the outbound coolant tubing 482.The first adapter 470 a has an internal coolant flow channel to allowthe coolant to flow from the first manifold to the outbound coolanttubing 482 through the first adapter 470 a. The second adapter 470 b hasa first side coupled to the first side of the second manifold, formed bythe third and fourth half structures 406 and 408, and a second sidecoupled to the inbound coolant tubing 480. The second adapter 470 b hasan internal coolant flow channel to allow the coolant to flow from theinbound coolant tubing 480 to the second manifold through the secondadapter 470 b.

Each of the inbound coolant tubing 480, outbound coolant tubing 482,first adapter 470 a, and second adapter 470 b is respectively made of anon-corrosive material. In one embodiment, each of the inbound coolanttubing 480 and outbound coolant tubing 482 is respectively made ofstainless steel, a nickel-plated metallic material, a gold-platedmetallic material, or a ceramic material. In one embodiment, at leastone of the first adapter 470 a and second adapter 470 b is made of astainless steel or ceramic material. The materials that the inboundcoolant tubing 480, outbound coolant tubing 482, first adapter 470 a,and second adapter 470 b are made of cannot be plastics or any materialsubject to corrosion when exposed to water. Chemicals leaching out ofplastics or particles coming off of a material due to corrosion, whenany of the inbound coolant tubing 480, outbound coolant tubing 482,first adapter 470 a, or second adapter 470 b is made of plastics or acorrosive material, will likely foul or clog up the internal coolantflow channels of the first manifold formed by the first and second halfstructure 402 and 404 as well as the internal coolant flow channels ofthe second manifold formed by the third and fourth half structures 406and 408.

In one embodiment, the inbound coolant tubing 480 and the outboundcoolant tubing 482 are respectively coupled to the second adapter 470 band the first adapter 470 a by solder, press-fit, epoxy bonding, orsingle-body machined. In one embodiment, the first and second adapters470 a and 470 b are coupled to the device 400 by solder or epoxybonding.

In one embodiment, the apparatus 4001 includes a coolant supplier 490 acoupled to the inbound coolant tubing 480 to supply the coolant at afirst temperature range, and a coolant receiver 490 b coupled to theoutbound coolant tubing 482 to receive the coolant at a secondtemperature range that is higher than the temperature range. In analternative embodiment, the coolant supplier 490 a and the coolantreceiver 490 b are part of a single heat exchanger system.

Illustrative Third Thermal Energy Transfer Apparatus

FIGS. 7-9 illustrate various views of a silicon-based thermal energytransfer device 700 for a right circular cylinder-shaped gain mediumcrystal 715 of a laser system in accordance with one non-limitingembodiment. The device 700 includes a first half structure 702, a secondhalf structure 704, a third half structure 706, a fourth half structure708, a first conduit element 750 a, and a second conduit element 750 b.Each of the first half structure 702, second half structure 704, thirdhalf structure 706, and fourth half structure 708 is made of silicon. Inone embodiment, each of the first half structure 702, second halfstructure 704, third half structure 706, and fourth half structure 708is metal-plated with a metal such as, for example, gold.

In one embodiment, each of the first half structure 702, second halfstructure 704, third half structure 706, and fourth half structure 708is fabricated from a respective silicon wafer using semiconductorfabrication technology including photolithography, dry etch, wet etch,etc. In one embodiment, the first half structure 702 and the fourth halfstructure 708 are identical, and therefore can be made by the samefabrication process and even be from the same silicon wafer. Likewise,in one embodiment, the second half structure 704 and the third halfstructure 706 are identical, and therefore can be made by the samefabrication process and even be from the same silicon wafer.

The first half structure 702 has a row of openings 746 as coolant outletports. As shown in FIG. 9, on one of the two primary surfaces of thefirst half structure 702, there are grooves 736 each of which associatedwith a respective one of the openings 746. The second half structure 704has a first row of openings 741 a and a second row of openings 741 b ascoolant inlet ports. As shown in FIG. 9, on one of the two primarysurfaces of the second half structure 704, there are grooves 738 each ofwhich connecting a respective pair of one of the openings 741 a and oneof the openings 741 b. The primary surface of the second half structure704 opposite the primary surface that has the grooves 738 has a groovebetween the rows of openings 741 a and 741 b to accommodate the crystal715.

In one embodiment, the thinnest part of the first half structure 702where the grooves 736 are, denoted as thickness T8 in FIG. 8, isapproximately a range of 100 to 200 μm.

The fourth half structure 708 has a row of openings 740 as coolant inletports. As shown in FIG. 9, on one of the two primary surfaces of thefourth half structure 708, there are grooves 737 each of whichassociated with a respective one of the openings 740. The third halfstructure 706 has a first row of openings 742 a and a second row ofopenings 742 b as coolant outlet ports. As shown in FIG. 9, on one ofthe two primary surfaces of the third half structure 706, there aregrooves 739 each of which connecting a respective pair of one of theopenings 742 a and one of the openings 742 b. The primary surface of thethird half structure 706 opposite the primary surface that has thegrooves 739 is substantially flat to provide surface area to contactwith the corresponding primary surface of the crystal 715.

In one embodiment, the thinnest part of the fourth half structure 708where the grooves 737 are, denoted as thickness T9 in FIG. 8, isapproximately a range of 100 to 200 μm.

As shown in FIGS. 7 and 8, the first half structure 702 and the secondhalf structure 704 together form a first manifold. The third halfstructure 706 and the fourth half structure 708 together form a secondmanifold. The first half structure 702 and the second half structure 704may be affixed to each other by solder, silicon-to-gold eutecticbonding, or silicon-to-silicon bonding. The third half structure 706 andthe fourth half structure 708 may be affixed to each other by solder,silicon-to-gold eutectic bonding, or silicon-to-silicon bonding.

The first conduit element 750 a has a cavity 744 a. The second conduitelement 750 b has a cavity 744 b. When the first and second conduitelements 750 a and 750 b are coupled between the first manifold formedby the first and second half structures 702 and 704 and the secondmanifold formed by the third and fourth half structures 706 and 708, thecavities 744 a and 744 b allow a coolant to flow through the first andsecond conduit elements 750 a and 750 b from the openings 742 a and 742b, which are the coolant outlet ports of the second manifold formed bythe third half structure 706 and the fourth half structure 708, to theopenings 741 a and 741 b, which are the coolant inlet ports of the firstmanifold formed by the first half structure 702 and the second halfstructure 704. In one embodiment, one or both of the first and secondconduit elements 750 a and 750 b are made of a metal-based material suchas, for example, copper, aluminum, or stainless steel. In oneembodiment, one or both of the first and second conduit elements 750 aand 750 b are made of a ceramic or silicon material.

As shown in FIGS. 7 and 8, when the right circular cylinder-shapedcrystal 715 is mounted between the first manifold formed by the firstand second half structures 702 and 704, the second manifold formed bythe third and fourth half structures 706 and 708, and the first andsecond conduit elements 750 a and 750 b, the side of the crystal 715 isin contact with the device 700, leaving the two circular primarysurfaces of the crystal 715 exposed to allow a laser beam to shinethrough. A filler material 720 fills the gap of space between thecrystal 715, the first and second half structures 702 and 704, thesecond manifold formed by the third and fourth half structures 706 and708, and the first and second conduit elements 750 a and 750 b. Thefiller material 720 has high thermal conductivity and promotes thetransfer of thermal energy from the crystal 715 to the device 700. Inone embodiment, the filler material 720 is a soft solder, indium, silverglass, or thermal epoxy.

FIG. 12 illustrates a thermal energy transfer apparatus 7001 thatincludes the silicon-based thermal energy transfer device 700 inaccordance with one non-limiting embodiment. The apparatus 7001 includesan inbound coolant tubing 780, an outbound coolant tubing 782, a firstadapter 770 a, and a second adapter 770 b.

The first adapter 770 a has a first side coupled to the first side ofthe first manifold, formed by the first and second half structures 702and 704, and a second side coupled to the outbound coolant tubing 782.The first adapter 770 a has an internal coolant flow channel to allowthe coolant to flow from the first manifold to the outbound coolanttubing 782 through the first adapter 770 a. The second adapter 770 b hasa first side coupled to the first side of the second manifold, formed bythe third and fourth half structures 706 and 708, and a second sidecoupled to the inbound coolant tubing 780. The second adapter 770 b hasan internal coolant flow channel to allow the coolant to flow from theinbound coolant tubing 780 to the second manifold through the secondadapter 770 b.

Each of the inbound coolant tubing 780, outbound coolant tubing 782,first adapter 770 a, and second adapter 770 b is respectively made of anon-corrosive material. In one embodiment, each of the inbound coolanttubing 780 and outbound coolant tubing 782 is respectively made ofstainless steel, a nickel-plated metallic material, a gold-platedmetallic material, or a ceramic material. In one embodiment, at leastone of the first adapter 770 a and second adapter 770 b is made of aceramic material. The materials that the inbound coolant tubing 780,outbound coolant tubing 782, first adapter 770 a, and second adapter 770b are made of cannot be plastics or any material subject to corrosionwhen exposed to water. Chemicals leaching out of plastics or particlescoming off of a material due to corrosion, when any of the inboundcoolant tubing 780, outbound coolant tubing 782, first adapter 770 a, orsecond adapter 770 b is made of plastics or a corrosive material, willlikely foul or clog up the internal coolant flow channels of the firstmanifold formed by the first and second half structure 702 and 704 aswell as the internal coolant flow channels of the second manifold formedby the third and fourth half structures 706 and 708.

In one embodiment, the inbound coolant tubing 780 and the outboundcoolant tubing 782 are respectively coupled to the second adapter 770 band the first adapter 770 a by solder, press-fit, epoxy bonding, orsingle-body machining. In one embodiment, the first and second adapters770 a and 770 b are coupled to the device 700 by solder, press-fit,epoxy bonding, or single-body machining.

In one embodiment, the apparatus 7001 includes a coolant supplier 790 acoupled to the inbound coolant tubing 780 to supply the coolant at afirst temperature range, and a coolant receiver 790 b coupled to theoutbound coolant tubing 782 to receive the coolant at a secondtemperature range that is higher than the temperature range. In analternative embodiment, the coolant supplier 790 a and the coolantreceiver 790 b are part of a single heat exchanger system.

Conclusion

The above-described techniques pertain to silicon-based thermal energytransfer for the gain medium of a laser system. Although the techniqueshave been described in language specific to structural features and/ormethodological acts, it is to be understood that the appended claims arenot necessarily limited to the specific features or acts described.Rather, the specific features and acts are disclosed as exemplary formsof implementing such techniques. Furthermore, although the techniqueshave been described in the context of laser systems using laser diodes,the techniques may be applied in any other suitable context.

What is claimed is:
 1. A thermal energy transfer apparatus that removesthermal energy from a disk-shaped gain medium crystal of a laser system,the apparatus comprising: a silicon-based manifold that has internalcoolant flow channels, a first side, and a second side opposite thefirst side, wherein: the first side includes coolant inlet ports andcoolant outlet ports communicatively connected to the internal coolantflow channels, and the second side is substantially flat to providesurface area to contact with a first primary surface of the crystal; anda silicon-based cover element that has an opening to expose a portion ofa second primary surface of the crystal that is opposite the firstprimary surface of the crystal when the crystal is mounted between thecover element and the manifold, wherein the cover element comprises: afirst plate made of silicon, the first plate having an opening smallerthan an area of the second primary surface of the crystal to expose aportion of the second primary surface of the crystal; and a second platemade of silicon, the second plate having an opening larger than the areaof the second primary surface of the crystal and shaped to at leastpartially circumscribe the crystal with the crystal contacting aplurality of points of the opening of the second plate when the crystalis mounted between the cover element and the manifold.
 2. The apparatusof claim 1, wherein the manifold comprises: a first half structure madeof silicon, the first half structure having a first primary surface thatis the first side of the manifold and a second primary surface oppositethe first primary surface, the first half structure having openings asthe coolant inlet ports and the coolant outlet ports of the manifold,the second primary surface having grooves that form a first half of theinternal coolant flow channels of the manifold; and a second halfstructure made of silicon, the second half structure having a firstprimary surface that is the second side of the first manifold and asecond primary surface opposite the first primary surface, the secondprimary surface having grooves that form a second half of the internalcoolant flow channels of the manifold.
 3. The apparatus of claim 1,further comprising: a layer of synthetic diamond on the second side ofthe manifold to be in direct contact with the crystal when the crystalis mounted between the manifold and the cover element.
 4. The apparatusof claim 1, further comprising: a plurality of nanotubes on the secondside of the manifold to be in direct contact with the crystal when thecrystal is mounted between the manifold and the cover element.
 5. Theapparatus of claim 1, further comprising: an inbound coolant tubing madeof a metallic or ceramic material; an outbound coolant tubing made of ametallic or ceramic material; an adapter made of a ceramic material, theadapter having a first side coupled to the first side of the manifoldand a second side coupled to the inbound coolant tubing and the outboundcoolant tubing, the adapter having an inbound coolant flow channel toallow the coolant to flow from the inbound coolant tubing to themanifold through the adapter, the adapter further having an outboundcoolant flow channel to allow the coolant to flow from the manifold tothe outbound coolant tubing through the adapter; and a heat exchangersystem coupled to the outbound coolant tubing and the inbound coolanttubing, the heat exchanger system supplying the coolant to the inboundcoolant tubing and receiving the coolant from the outbound coolanttubing to remove thermal energy from the coolant.